Circuit arrangement for all-relay connector switch composed of tens and units relays



O 1955 K. KLINKHAMMER ET AL 2,719,880

CIRCUIT ARRANGEMENT FOR ALL-RELAY CONNECTOR SWITCH COMPOSED OF TENS AND UNITS RELAYS Filed April 3, 1952 2 Sheets-Sheet l Co l NQ TT Ni u w a H N R O T T A INVENTOR K. KLI NKHAMMER I A. MEHLIS Oct. 4, 1955 K KLINKHAMMER ET AL 2,719,880

CIRCUIT ARRANGEMENT FOR ALLRELAY CONNECTOR SWITCH COMPOSED OF TENS AND UNITS RELAYS Filed April 5, 1952 2 Sheets-Sheet 2 INVENTOR KKUNKHAMMER A. MEH LfS BY ATTORNEY United States Patent CIRCUIT ARRANGEMENT FOR ALL-RELAY CON- NECTOR SWITCH COMPOSED OF TENS AND UNITS RELAYS Kurt Klinkhammer and Arthur Mehlis, Stuttgart-Zuffenhausen, Germany, assignors to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application April 3, 1952, Serial No. 280,336 Claims priority, application Germany April 7, 1951 Claims. (Cl. 179-18) A growing tendency in communication systems, in particular telephone systems, due to the particular conditions of subscriber toll dialing, goes towards replacing the more or less complicated mechanically operating selector switches by so called all-relay switches which are less susceptible to trouble, have short setting times, and offer advantages from the transmission angle because instead of the base metal used on wipers, contacts of noble metals can be used which secures better and more reliable contacts.

It is known to compose such a connector switch from one tens and one units relay group, and to eifect the connection with any given terminal of the connector switch by a relay combination including a tens and a units relay. The connector switches of this kind have the denierit that, unlike the way known in the Strowger switch principle, their control is not effected immediately by the pulse trains set by the calling subscriber, but extra control mechanisms, such as registers and counting chains, are required, part of which equipment is individual, part common, to all terminals. The known all-relay systems are thus rather expensive, which may be highly contributory to the fact that such systems have not made their entrance in the field so far, in particular that they have not been used for large size plants.

The invention relates to a circuit arrangement for an all-relay line connector switch composed of tens and units relays, which is characterized by the fact that layout and control of these connector switches are in analogy to the Strowger selector principle. This introduces the considerable advantage that such a relay system has all those favorable characteristics which are inherent in the Strowger selector system, and that they are readily compatible with existing systems of this kind.

In accordance with the invention, the connector switch is designed in a way that for setting the connector switch both trains of pulses are fed to the units relay group which, upon reception of the first train of pulses, transfers its setting to the tens relay group, and which, after its subsequent release, is set ultimately by the second train of pulses.

In accordance with a further characteristic of the invention, the tens relay group is composed from multicontact relays. From the angle of circuitry, advantages are obtained, when in accordance with one more characteristic of the invention the multi-cont'act relays of the tens relay group are designed as two-step relays.

In analogy to the Strowger switch system, a connector switch made in accordance with the invention can be readily provided with a PABX hunting feature, if, in accordance with another characteristic of the invention, terminals of the connector switch identical in their units digits but differing in their tens digits, are combined to form a PABX trunk group. Herewith it is readily possible in grouping terminals to skip individual or several decades (levels) and to assemble the skipped-over decades to one more PABX group.

2 ,719,880 Patented Oct. 4, 1955 The invention will be explained in the following with the aid of the embodiment shown in the drawings, in which Fig. 1 shows a circuit arrangement of a connector switch in accordance with the invention, while Fig. 2 shows the circuit of the units relay group which in Fig. 1 has been omitted for clarity, and which has to be inserted between the terminals K and K1 of Fig. 1. The action of the connector switch is as follows:

In the drawings the contacts for the relays are not shown adjacent their respective relays but in the circuits which they control. The relays are identified by upper case letters, while their contacts are identified by corresponding lower case letters followed by a roman numeral indicating the number of the contact. Contacts of the relay A, for example, are represented by aI, aII, aIII, etc. Also certain of the relays have more than one winding. Each of the windings are represented by a rectangle with the letter of the relay adjacent to it and the number of the winding within the rectangle. Winding No. II of the H relay, for instance, is shown at the lower left hand corner of Fig. 1, while the winding No. I is shown at the lower center of Fig. 2.

The connector switch is seized by way of the input cg. In the seizing circuit which passes over minus potential in the preceding switching stage, cg, W1, cI, yI, 1111, r1, A(I), uIII, ground, the relay A operates which with its contact all connects and operates the relay H(H). In the so completed circuit minus battery, W3, C, aI or v1, p11, k1, W5, 011, plus battery, (ground), the relay C energizes which with its contact cl blocks the line connector against double seizure. After the winding I of relay A has been disconnected by contact cl, the pulse-repeating and feed relay A holds with its windings II and III over the calling subscriber loop. The relay H, the winding II of which had been disconnected by contact cII, holds on in the following circuit: minus battery, W2 (Fig. 2), contact chain eltlIII to elIIl, hIII, H(I), terminal, K1, uIV (Fig. 1), cIII, plus battery, (ground). Since contact hI opens, relay V is energized.

The units relay group is controlled by the train of incoming pulses repeated by the relay A in the following manner:

As relay A falls back for the first time, the following circuit is completed: minus battery (Fig. 1), W3, pIII, vV, aIII, terminal K, E1(II) of Fig. 2, hV, hIII, H(I), terminal K1, uIV (Fig. 2), cIII, plus battery, (ground).

In this circuit, relay E1(II) is energized which with its contact e1 II prepares a locking circuit. When relay A operates again to open its contact aIII, the aforementioned circuit is interrupted again. The relay H which had held by way of the chain of contacts elIII to elOIII, restores due to opening of contact ellll, and by its contact hI it prepares a pulsewise short-circuit of relay V, so that after the train of pulses has terminated, it can fall back in a slow-release manner. As relay A falls back next (second pulse), the pulse circuit is completed once more, so that relay E2 (II) of Fig. 2 is energized by way of contact elI in the circuit: minus battery, W3 (Fig. 1), pIII, vV, aIII, K, E2(II) of Fig. 2, ell, 121V, @111, E1(I), K1, ulV (Fig. 1), e111, plus battery, (ground). Contact e2ll completes a locking circuit by way of winding I of relay E2. As contact eZlII opens, the holding circuit of relay E1(I) is interrupted. As soon as relay A re-energizes upon termination of the pulse and thus opens its contact aIII, relay E1 restores. This interplay repeats in step with the incoming pulses in a way that, for instance, when the digit 6 is being dialed, the further progress is as follows: relay E3 operates and relay E2 restores, relay E4 operates and relay E3 restores, relay E5 operates and relay E4 restores, and finally relay E6 energizes and relay E5 restores.

There are ten tens relays, Z1 to Z10, although relays Z4 to Z9, inclusive, have been omitted from the drawing to save space. When, at the end of the train of pulses, relay V restores, it is, in the assumed case, the tens relay Z6 which is energized in the following circuit: minus battery, W6, z10vh to z6vh (not shown), 26(1) (not shown), 261V (not shown), rlV, uV, clV, vlV, clII, plus battery, (ground). The tens relays Z1 to Z10 are designed as two-step relays. In the aforementioned circuit, relay Z6 energizes in its first step, so that only the pilot contact z6vh of the first step is actuated. By way of winding II of relay Z6, this contact effects a holding circuit which includes the resistor W8, and in which the tens relay is held energized in its first stage.

After relay V has de-energized, relay U of Fig. 1 operates slowly in the circuit: minus battery, W3, yll, U/ W4, W9, vVI, hll, pIV, 0111, plus battery, (ground), and locks itself over its contact ulV. As contact uIV transfers, ground is withdrawn from the terminal K1 of the units relay group of Fig. 2, so that the units relay held so far- E6 in the assumed caserestores. By energization of relay U relay H is energized in the circuit: minus battery, H(II), rlll, uV, clV, vIV, cllI, plus battery, (ground), so that relay V re-energizes due to the lifting of the short at contact hl. After relay V has re-energized, relay H holds in the circuit mentioned above. This prepares the units relay group for the reception of the second train of pulses.

The incoming pulses of the second train of pulses are received in the manner described above by the units relay group of Fig. 2. Let us assume that the calling subscriber sends 3 pulses. Then at the end of the train of pulses relay E3 energizes and is held energized. As in receiving the first train of pulses, relay H restores in the second train of pulses at the end of the first pulse, and prepares the short-circuit of relay V. At the same time, relay R energizes in the following circuit: minus battery, R(I), uVI, vVI, hII, plV, clll, plus battery, (ground). After termination of the second train of pulses, relay V restores, while, by way of contact rll the energization of the selected units relay-E3 in the assumed case-is maintained. When relay V restores, the resistor W3 is shorted by contact viV, so that the current for the tens relay Z6, which had been energized so far at its first step, is increased, and this relay now pulls fully up and connects its contacts at the terminals of the connector switch. The increased current circulates over: plus battery, (ground), cill, vIV, 01V, 11V, rllI, Z6(ll) (not shown), z6vh (not shown), to zltivh, W6, minus battery.

Even when the by-pass of the resistor W8 is lifted later on, the tens relay holds on at its second step. A contact of the tens relay Z6 short-circuits the winding of relay U by way of 61, vV, pill, yll, and thus effects a busy test time limit to the busy test relay P, which receives a testing ground for the time relay U has been energized.

The busy test is effected by way of the outgoing wire c1. If relay P fails to operate during the predetermined test period, relay R remains held in the circuit minus battery, R(l), rVl, plV, clll, plus, (ground), and the calling subscriber receives a steady signal tone over its feed relay A which is fed by a 450-eycle note by way of plus battery, (ground), ulil, A(l), rI. If however the busy test relay P operates during the test period, the short-circuit around relay U is cut at the contact pill, and relay U holds on.

Contact pH lifts the short-circuit of the relay V, so that this relay re-energizes and provides with its contact vIV for the ground at the terminal K1 of the units-relay group, which had been effected so far by the contact rII. The winding I of relay R is disconnected by contact 21V and ground is applied to the relay R from the IO-second timer by way of p111, R(II), 1111.

The talking leads of the connector switch are held open under control of contact pIV. The dialed subscriber is called in the usual manner at the rate of the l-second timer.

When the called subscriber answers, relay Y energizes to interrupt with its contact yII the holding circuit of relay U which restores and cuts oif the ring. When relay R has restored, the talking circuit is through-connected.

When at the end of the conversation the calling subscriber replaces his set, relay C is short-circuited by contact aI, and it releases the relay V when it has restored. The busy-test relay as well as the energized tens and units relays are held operated by contact yIlI, until the called subscriber has replaced his instrument which restores relay Y, and the remaining relays still energized at this stage return to normal.

If the called subscriber is the first to replace his set, relay Y restores and shorts relay C by way of: yII, uI, pII, aI. By relay C restoring, the connector switch is released.

The shown and described circuit arrangement can be modified in such a way that the relay U, short-eircuited to limit the busy-test period, restores at the end of the test period by a short-circuit. The circuit can also be modified in such a way that relay V is not re-energized by relay P operating but only after the called subscriber has answered.

On the connector switch of Figs. 1 and 2, PABX groups can readily be assembled. To this end, the wires indicated with a cross in Fig. 1 are provided. Before we enter into a discussion of the detailed switching action, it may be remarked that for PABX groups there are assembled those terminals which have identical units digits, but different tens digits. There can thus be grouped as a PABX group, for instance, the terminals 35, 45, 55, etc. It is however readily possible to skip individual or several decades (levels), so that, for instance, the terminals 35, 65, 85, 95 may be grouped to form a PABX group. Finally, it is even feasible to assemble the skipped decades as one more PABX group, so that there may be assembled, for instance, for the first PABX group the terminals 35, 65, and for the second PABX group the terminals 45, 55, 75, 95. A high amount of freedom exists thus in assembling terminals to PABX groups.

In the following there will now be explained the action which occurs when the connector switch is directed to a busy PABX trunk. Let us assume that the terminals 15, 25, 35, etc. up to 05 have been assembled into a PABX group. To reach this PABX group, the calling subscriber dials the directory number 15, and at the end of the dialing the tens relay Z1 and the units relay E5 are energized. It will now be assumed that the terminal 15 is busy, so that the relay P cannot operate and relay U thus restores. There is thus completed the following circuit: plus battery, CHI, vIV, 11V, eSV, 2111, 22(1), z2vh W6, minus battery.

In this circuit relay Z2 pulls up to its first step, and by transfer of its pilot contact z2vh it cuts the holding circuit of relay Z1. As this relay restores, the short-circuit of relay U is lifted, so that it re-energizes and boosts the current with its contact uV which makes the tens relay Z2 pull fully up, so that there is once more test potential applied to the busy test relay P. As the tens relay Z2 pulls fully up, relay U is short-circuited again and restores slowly, in case the test relay P has failed to energize during this release time.

The connecting action continues with respect to the further terminals in case the second trunk 25 of the PABX group turns out to be busy. If it is assumed that the busy test relay operates after the tens relay Z3 has operated and pulled up fully, contact pHI removes the short-circuit from relay U and p11 removes the shortcircuit from relay V. Relay U thus remains energized, and relay V operates, so a further stepping of the switch to the next trunk of the PABX group is suppressed. The further action then takes place in the manner described above.

What is claimed is:

1. A circuit arrangement for an all-relay connector switch having tens and units storing relays comprising, in combination, means for receiving successive trains of pulses representing, respectively, tens and units digits, means controlled by said receiving means when a train of pulses is received for setting said units storing relays in accordance with the pulses of the received train, means for transferring the setting of said units storing relays into said tens storing relays, circuit means for operating said transferring means, means controlled by the operation of said units storing relays for preparing said circuit means, means responsive to the end of the first pulse train for causing said circuit means to operate said transfer means, and means controlled by said transfer means for releasing said units storing relays so that they may be set up by said second train of pulses.

2. A circuit arrangement, as claimed in claim 1, in which the tens storing relays are multi-contact relays.

3. A circuit arrangement, as claimed in claim 2, in which the multi-contact relays of the tens relay group are two-step relays.

4. A circuit arrangement, as claimed in claim 3 in which the means for transferring the setting of the units storing relays to the tens storing relays causes the selected tens storage relays to operate to the first step.

5. A circuit arrangement, as claimed in claim 4, further comprising means for maintaining the energization of the selected tens storing relay in its first step after the units relays have been released.

6. A circuit arrangement, as claimed in claim 5, further comprising circuit means for causing the selected tens storing relays to operate to their second step, means responsive to the initiation of the second train of units pulses for preparing said circuit means for operation, and means responsive to the end of said second pulse train for causing the operation of said circuit means.

7. A circuit arrangement, as claimed in claim 6 in which the group of units storing relays has three input terminals, further comprising a circuit for the relay setting means, means for completing said circuit over two of said input terminals, an independent source of potential, and means for applying said potential to said group of storing relays over said third input terminal for providing holding circuits for said relays.

8. A circuit arrangement, as claimed in claim 7 in which the connector switch has a plurality of terminals, said terminals representing the units digits and tens digits, and in which terminals of identical units digits and different tens digits are connected to form a PABX group.

9. A circuit arrangement, as claimed in claim 8, in which means is provided to operate the tens relay of the next trunk of the PABX group in case the trunk of said group corresponding to the first dialed number is busy, and means for simultaneously restoring the tens relay of the trunk corresponding to said previously dialed number.

10. A circuit arrangement, as claimed in claim 9, further comprising means controlled by the busy condition of the line of a PABX group to which the switch is connected for causing the tens relay of the next following line of the PABX group to operate to its first step and to release the tens relay of the preceding line of the PABX group, whereby when said first named relay operates to its second step, the testing of the second line of the PABX group is initiated, and means for repeating the above action if said second line is busy.

References Cited in the file of this patent UNITED STATES PATENTS 

